Electric switch



'June 30, 1931 J. D. HILLIARD 1,812,746

ELECTRIC SWITCH Filed July 11, 19215 e. c q

'Umllllllll Patented June 31), 1931 UNITED srA'rl-:s PATENT oFFlcE i IOHN D. HILLIARD, OF SCHENECTADY, NEl' YORK, ASS'IGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC SWITCH Application led July. 11, 1927. Serial No. 204,674.

My invention relates to electric switches of the fluid break type and partmularly to the vessel or casing which confines the switch contacts and the insulating liquid in which they are immersed.

In the normal interrupting operatlon of a modern oil switch such as is commonly used for controlling power distribution circuits the switch draws a relatively small arc between the fixed and movable contacts .resulting in the decomposition of a certain amount of the oil into gas. The amount of gas thus formed is dependent upon the duration of the arc and load 'current which is interrupted. Oil switches in the past commonly have been providedl with a gas discharge passage of a size that was calculated to safeguard the vessel from rupture under all ordinary operating and overload conditions.- It has sometimes happened, however, that the operation of the switch has been accompanied by an objectionable oil discharge, particularly when opening the circuit under a heavy overload or short circuit. A discharge of hot oil and gas in the vicinity of the switch is a well known source of danger both to the station operating force and to other adjacent apparatus. Moreover, upon the possible occurrence of a sudden pressure in the tank far in excess of that which the discharge means can relieve, due for example to an internal breakdown of insulation or to a failure of the switch, a rupture of the vessel may occur spreading disaster in all directions.

An object of my invention therefore is to provide an improved enclosingvessel for an electric switch ofthe fluid break type having means for confining and releasing pressure formed therein in a manner such that the above mentioned objections and dangers shall be materially reduced if not entirely eliminated. In accordance with my invention I provide the enclosing vessel with but a relatively small gas vent, the casing being otherwise tight, thereby to prevent the throwing of oil and construct the vessel to have sulliN cient strength to withstand the pressure developed therein due to ordinary operation of the switch if all the gas is retained. I also provide the enclosing vessel at a point above the liquid level with a relatively large capacity discharge or pressure relief opening which normally is closed by a member having small mass and which upon the occurrence of a predetermined pressurein the tank will quickly release the pressure allowing it to escape freely through the discharge opening provided therefor.

My invention will be better understood from the following description taken in connection with the accompanying drawings, and

its scope will be pointed out in the appended claims.

Referring to the drawings, Fig. 1 is a top view of a triple oil switch involving my invention; Fig. 2 is a detail cross sectional view of the upper portion of one switch unit with the oil separating and venting arrangement drawn to a larger scale; and Figa shows a modification.

In the drawings each switch unit l coniprises fixed and movable contacts (not shown) adapted to separate beneath the surface of an insulating liquid sach as oil within the enclosing vessel 2. This vessel preferably comprises the top or cover 8, through which extend the insulator bushings 4, and a tank not shown) firmly secured to and detachable from the cover. The. vessel lisprovided with suitable gaskets at the points where the tank joins the cover' and where the operating rods or the like pass through the cover. The operating mechanism is indicated dia-grammatically at 3: Fig. l. The vessel is con-- structed to withstand with safety the maximum pressure which occurs due to gas formation therein as a result of interrupting circuits for which it is designed. The casing 6, in the embodiment of my invention illustrated, is shown mounted on top of the coverv 3 and clamped thereto by suitable means shown as screws 7 with an intervening gasket 8. It has a relatively large relief passageway 9 therein connecting with the interior of the vessel 2 and shown arranged centrally of' den and unrestricted relief of pressure in the vessel. For this purpose I have shown the concavo-convex diaphragm or plate member 11 mounted, as for example by soldering in the ring l2, which is screw-threaded or otherwise secured into the passage 9. The ring is provided with slots 13 by which it may be turned and has an internal flange 14. Member 11 is arran `ed with its convex face inward and with its edge engaging the ange and the inner face ofthe ring. Preferably its form is spherical and its diameter substantially equal to its radius of curvature. As such, the pressure at which it ruptures may be calculated from the formula where P is the pressure, K is a constant, T is the thickness and I) is the diameter. The construction of the diaphragm member 11 and its mounting is disclosed and claimed in the copending application of William K. Rankin (Serial No. 204,687) filed July 11, 1927 and assigned to the same assignee as the present application. It is preferably a ductile sheet metal plate such as annealed copper and is constructed to withstand all such pressures occurringin t-he breaker incident to the interruption of the circuits for which the breaker is designed under normal load, overload, or short circuit conditions. If, however, there should occur in the enclosing vessel a greatly increased pressure such as might result from a failure of the switch to interrupt the circuit or an internal breakdown of insulation which pressure might rupture the enclosing vessel, the member 11 will immedately give way to the pressure and allow a rapid and unrestricted escape of gas and insulating liquid. Inasmuch as t-he disk is of light construction its deformation having once begun takes place with great rapidity i and having had its convexity reversed it is easily blown past the iange 14 and out of the discharge opening into pipe 15. This pipe may lead to a distant point where no damage can be done to the switch or to other apparatus and preferably exhausts into a large #mass of gravel where the gas and liquid are ment is, for example, disclosed and claimed in my application Serial No. 52,669 filed August 25, 1925 and assigned to the same assignee as the present invention. Renewal of the member 11 is effected by first removing the screw plug 16 which closes the outer end of the threaded portion when by the use of a suitable tool engaging the slots 14 the ring 13 may be screwed out and a new ring and member 11 may be screwed into place. Vhere the lateral portion of the passage 9 joins the threaded portion, it is made oval in shape with the short axis horizontal and less than the diameter of the threaded portion so as to provide a threaded portion of suiiicient circumferential extent to retain the ring 13 as it is inserted in or removed from the passage.

As has already been described the switch which I have devised is intended to operate normally as a completely closed switch. By that I mean that no substantial amount of gas escapes during the period of gas formation. Inasmuch as the switch may soon be called upon for a subsequent operation or operations, I have provided for the escape of the internal pressure through a small escape opening 20. In Fig. 2, I have shown this opening formed in the nipple 21 threaded into the bottom of the casino' 6 and communieating with the chamber through the screen 22. The outlet of chamber 1() is through the nipple 23 which discharges into the threaded portion of the passage 9. I have shown the nipple having a number of small entrance openings and as secured in place by the plug 24. By this construction the highly heated gas produced by each operation of the breaker gradually is conducted around the member 11 closing the relief passage 9 and after being cooled and separated from any liquidthat may accompany it is passed into the outer portion of the passage 9 whence it is carried away by the pipe 15. The size of the opening 20 for the most satisfactory results will depend to a certain extent upon the capacity of the breaker. I have obtained very good results where the opening has been made about one quarter of an inch in diameter. The end of the nipple 21 preferably is extended somewhat below the inner face of the top 3 thereby lessening the amount of liquid which being thrown up against the cover 3 will enter the opening 20.

llnder certain circumstances it may be^de sii-able to provide the top 3 with but a single opening for both outlets. In the modified form comprising Fig. 3, I have shown the casing 25 having the nipple 26 which is screwedinto the top 3 and the pipe 27 having an opening therethrough similar to that in the nipple 21 Apassing into .the discharge opening 9 thence into the cooling chamber 10 by means of a perforated nipple like that shown for the outlet in Fig. 1. To avoid clogging the pipe 27 with a slug of liquid which may be thrown up vinto the discharge opening 9, I extend the pipe 27 to a point somewhat below the end of the casing nipple 26.

Connected into the pipe 15 I have shown a pressure operated device for giving a signal of the blowing out of a diaphragm by the closing of a circuit. The small cylinder 30 having a spring pressed piston therein is screwed into the pipe 15 and on the cap of the cylinder is mounted the lever 31 which carries the contact 32 and to which is pivoted the piston rod 33. Resilient member 34 rctains the lever 31 in raised position with its contact connecting the contacts 35 of the signal circuit when the pressure in the pipe 15 operates the piston. When there are a number of breakers connected by the same discharge piping each device is adjusted to respond only to the discharge of the breaker to which it is directly associated.

" Inasmuch as the diaphragm 11 is relatively weak to oppose pressure applied to its concave face., I have found it desirable, particularl'y where several switch units of a switching equipment have their outlet pipes 15 connected to a common manifold 37 as shown in F ig. 1, to employ a second diaphragm 38 similar to diaphragm 11 and attached to the -saine ring 12 but at the opposite side of iange 14 and convexed outwardly. This second diaphragm 38 will thus oppose the back pressure from some other switch unit but will not materially interfere with the quick relief of pressure'in the switch unit to which it is aplied.

p Spaced below the top 3 I preferably provide a suitably supported balile 40 which is arranged to shield the passageway 9 as well as the opening 20 from a mass of oil that may be thrown up against the top when the circuit is opened by the switch. I have shown the batlie 40 secured to the top by means of bolts 41 around which are the spacing sleeves 42.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric switch adapted to interrupt a circuit beneath the surface of an insulating liquid, a closed vessel for said liquid, a hollow member secured thereto providing a large relief passage in communication with the interior of the vessel, a member normally closing said passage, said hollow member having a relatively small pressure escape passage therein also in communication with the interior of the vessel and in communication with said reliefpassage arranged to bypass said closing member, the member normally closing the relief passage being constructed to be blown bodily free from the passage in response to a predetermined pressure in the vessel.

2. An electric switch adapted to interrupt a circuit beneath the surface of an insulatin liquid, a closed vessel containing said liqui a casing secured to said vessel having a. 'plurality of passageways therein each communieating with the interior of the vessel, one of the passageways being relatively large and being normally closed, the other of said passageways having a relatively small entrance connection with the interior ot' the vessel and containing cooling material through which gas under pressure i' rom said vessel may pass.

3. An electric switch adapted to interrupt acircuit beneath the surface of an insulating liquid, a closed vessel containing said liquid, a casing attached to the top of said vessel ha viuga relatively la rgc pressure. relief passage therethrough, a light. bodily displaceable member normally closing said passage, said casing comprising a chamber having a restricted inlet opening communicating with the. interior of the vessel and an outlet opening communicating with said passage beyond sai-d member, and gas cooling means in said chamber. 4. An electric switch adapted to interrupt a circuit beneath the surface of an insulating liquid, a closed vessel containing said liquid, a member secured to the top of said vessel providing a normally closed relatively large discharge passage for the vessel and providing a normally open relatively small gas escape passage, the entrance to the small passage being spaced below the entrance to large passage and a pipe communicating with the outlets of both passages.

5. An electric switch adapted to interrupt a circuit beneath the surface of an insulating liquid, an enclosing vessel for the liquid, a casing secured thereto'having a large relief passage, a supporting ring detachably secured in said passage, an inwardly convexed diaphragm mounted in said ring, said casing having a passage for the slow escape of gas from the vessel leading into said relief passage beyond said diaphragm.

6. An electric switching equipment comprising a plurality of enclosing vessels each adapted to interrupt a circuit in insulating liquid, a manifold having a connection with each of said vessels, and a plurality of oppositely arranged concave-convex diaphragme in each of said connections arranged with their concave sides toward each other.

7. An electric switch comprising a plurality of enclosing vessels each adapted to interrupt a circuit in insulating liquid, means secured to each vessel providing a relatively small opening for the escape of pressure from the vessel and providing a relatively large relief opening for a quick discharge from the vessel," a manifoldhaving connections with the openingsof said vessels and pressure resisting means comprising a pair of concaveconvex diaphragms arranged with rtheir concave faces toward each other in each of said relief openings. n

8. An electric switch adapted to interrupt e, circuit beneath the surface of an insulatino liquid, an enclosing vessel for said liquid 'comprising a cover having a, pressure relief opening therein, a, eoncavo-Qonvex dia.- 5 phragm mounted in said opening with its convex face inward and adapted in response to a predetermined pressure in the vessel to reverse and be blown out, andmeanscomprising a baille for shieldino said diaphragm i0 rom the 'direct impact;` o? e mass of said liquid.

In Witness whereof, 'I have hereunto set my hand this 6th day of'July 3.927.

mi JOHNV HILLIARD. 

